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Öğe DISSOLUTION KINETICS OF ULEXITE PREPARED UNDER DIFFERENT CALCINATION TEMPERATURES(Springer Heidelberg, 2008) Demirkiran, N.; Kunkul, A.Ulexite is one of the boron minerals used as a raw material in the production of boron compounds. It contains a substantial amount of hydration water. Using calcination methods, the B2O3 grade of ulexite can be increased. In this study, the effect of calcination temperature on dissolution kinetics of ulexite in ammonium chloride solutions was investigated in a batch reactor employing the parameters of concentration, solid-to-liquid ratio and reaction temperature. It was found that the dissolution rate increased with increasing concentration and reaction temperature and with decreasing solid-to-liquid ratio. The highest dissolution rate was obtained with the sample calcined at 413 K. It was determined that the dissolution rate fit to the second-order pseudo-homogeneous model. The activation energy of this dissolution process was found to be 64.3 kJ/moL.Öğe Dissolution of ulexite in ammonium carbonate solutions(Pleiades Publishing Inc, 2011) Demirkiran, N.; Kunkul, A.The dissolution of ulexite in ammonium carbonate solutions is investigated. The effect of concentration, particle size, stirring speed, and reaction temperature is examined. It is found that the dissolution rate increases with increasing concentration and reaction temperature, and with decreasing particle size. No effect of stirring speed was observed on the conversion. It is determined that the dissolution rate fits to the first order pseudo-homogeneous reaction model.Öğe LEACHING OF MALACHITE ORE IN AMMONIUM SULFATE SOLUTIONS AND PRODUCTION OF COPPER OXIDE(Brazilian Soc Chemical Eng, 2015) Ekmekyapar, A.; Demirkiran, N.; Kunkul, A.; Aktas, E.Malachite ore is one of the most important of oxidized copper ores. Copper production can be performed by using this ore. In this work, the leaching kinetics of malachite in ammonium sulfate solutions was investigated, and metallic copper was recovered by a cementation method from the resulting actual leach solution. Copper (II) oxide was prepared by an isothermal oxidation method from the cement copper. In the leaching experiments, the effects of reaction temperature, particle size, and stirring speed on copper leaching from malachite ore were studied. In the cementation experiments, metallic zinc was used as the reductant metal to recover the copper from the solution. Thermal oxidation of cement copper was performed under isothermal conditions. It was found that the leaching rate increased with increasing stirring speed and temperature, and decreased with particle size. It was observed that the leaching reaction fit to diffusion through the product layer. The activation energy of the leaching process was determined to be 25.4 kJ/mol. It was determined that the copper content of the metallic product obtained by the cementation method increased up to 96%. It was found that copper oxide prepared from cement copper had a tenorite structure.
